High-efficiency bulk photovoltaic effect with ferroelectric-increased shift current.

Abstract

Bulk photovoltaic (BPV) effect primarily stems from shift currents in symmetry-breaking materials, providing the potential to smash the Shockley-Queisser limit that constrains the performance of conventional p-n junctions-based solar cells. However, limited open circuit voltages (V_oc) or short circuit current densities (J_sc) from BPV devices still cause a low photoelectric conversion efficiency. Here, combining theoretical analysis and experimental evidence, we identify a range of BPV materials where both V_oc and J_sc can be co-optimized, and greatly boost the efficiency through ferroelectric engineered shift current. We select ferroelectric NbOBr₂ as an example and construct a two-dimensional in-plane device with a giant shift current-dominated BPV effect. In spontaneous polarization state, the devices demonstrate a record-high J_sc among all ferroelectric materials. Moreover, the electrically aligned NbOBr₂ polarization enables the significant co-enhancement of both V_oc and J_sc, leading to a colossal improvement of photoelectric conversion efficiency up to four orders of magnitude (1.25%), which is approximately four times greater than that of state-of-the-art BPV devices. Our work provides a promising solution for screening and creating higher efficient BPV cells.